Lung/chest expansion contributes to generation of pleasantness associated with dyspnoea relief.

Pleasantness associated with dyspnoea relief or 'respiratory pleasure' is considered as a particular sensory experience. The purpose of this study is to elucidate the mechanism of generation of this particular sensory experience. After taking deep breaths during normal breathing, 35 healthy subjects received three different magnitudes of inspiratory loads (light: 8.4; moderate: 23.4; severe: 70.5 cm H2O/L/s) to induce dyspnoeic sensation. We found that (1) deep breaths during normal breathing rarely induce 'respiratory pleasure', (2) a sudden removal of dyspnoea alone is not sufficient to produce 'respiratory pleasure', and (3) the generation of 'respiratory pleasure' can be observed when a sudden removal of dyspnoea accompanies a large increase in tidal volume (V(T)). In addition, qualitative assessment of 'respiratory pleasure' showed that this sensation is compatible with a strong, positively valenced sensation. These findings indicate that an increase in V(T) after removal of respiratory loading plays a crucial role in generation of 'respiratory pleasure' that is a specific sensory-emotional experience.